Efficiency Improvement and Ripple Suppression Method Based on Partial Power Processing for Wireless Power Transfer System

For a conventional wireless power transfer (WPT), two-stage structure is one of the most common topologies, of which the efficiency will be dramatically decreased by a cascaded dc-dc converter. In this article, a partial power processing structure for WPT system is proposed to improve the system efficiency and reduce output ripple. The receiver is divided into the main receiver and the auxiliary receiver. Most of the power is transferred to the load through the main receiver, whereas the auxiliary receiver is used to regulate the output voltage. As a result, the switching loss and device stress of the dc-dc cascaded at receiver can be significantly reduced. Besides, the optimal switching phase can be obtained by analyzing the output waveforms of two receivers to minimize the output ripple. A 500-W prototype is built to validate the feasibility of the proposed system. With the same output capacitor, controlling the switching phase can reduce the output ripple by 36% compared with that without the control. The processing power of the proposed system is from 4% to 29% when the input voltage changes from 190 to 250 V. The efficiency is improved by 2.4% compared with the two-stage structure under the same input and output conditions.